Steam Bending Longerons

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builderwannabe
Posts: 4
Joined: Mon May 13, 2019 8:05 pm

Steam Bending Longerons

Post by builderwannabe » Mon Sep 02, 2019 10:19 am

All, I have started building the fuselage and originally planned(because I assumed it was obvious) to steam bend the longerons. I could not find anything in the book that came with the plans about steam bending the longerons just the cap strips. After I built the fuselage side jig I found that the bottom longeron bent into place without issue. Even though I could glue it like this in my mind there would always be tension in the truss as the bottom longeron tried to unbend back to being straight. I know the epoxy will hold I am just worried that after years(decades) that the epoxy could fail. I was also not sure if there were any problems with the fuselage being under that tension and having a hard landing. Are there any thoughts on whether Mr. Pietenpol originally steam bent the longerons or just bent them into the form dry?

Sean

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Clay Hammond
Posts: 28
Joined: Thu Feb 23, 2017 11:46 am

Re: Steam Bending Longerons

Post by Clay Hammond » Mon Sep 02, 2019 10:44 am

Tangential to your question, but great way to steam bend here from 3:15 mark onward:

https://www.youtube.com/watch?v=7JFePos8RQQ
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EAB4
Posts: 59
Joined: Mon Mar 06, 2017 2:08 pm

Re: Steam Bending Longerons

Post by EAB4 » Tue Sep 03, 2019 7:43 am

Sean, this really isn't an issue, as far as i know, all of Bernards planes were formed dry- the bend is not that great to have to steam the longeron. There is not enough tension there to cause any problems (long or short term) and the side sheeting also holds it in that position.

Not a problem to keep you up at night! Put the longerons in the jig and get gluing!

Earl

builderwannabe
Posts: 4
Joined: Mon May 13, 2019 8:05 pm

Re: Steam Bending Longerons

Post by builderwannabe » Thu Sep 05, 2019 7:44 pm

Gents, thanks for the info, it helps to bounce ideas off of others, I’ll start slathering on the T-88 tomorrow.
Sean

Tools
Posts: 17
Joined: Wed Feb 22, 2017 9:22 pm

Re: Steam Bending Longerons

Post by Tools » Mon Sep 09, 2019 6:24 am

To further put your mind at ease...

Years ago I broke my lower longerons right there in the curve. I scarfed new longerons on right there using the normal 15:1 taper, but without scarf plates and dry bent them right back into place.

The joints are readily visible and easy to inspect. Despite the tension and years since, even in very hot weather, there has been no movement in the scarf joints whatsoever. I used T-88.

Tools

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